Strand heating apparatus

ABSTRACT

A heater for a false twist machine. A strand of yarn passes in a circuitous path through the heater and over guides which provide a fluid cushion supporting the strand.

United States atent 1151 3,641,756

Keith et al. 5] Feb. 15, 1972 54 STRAND HEATING APPARATUS 3,449,898 6/1969 Fujita et a1 ..57/34 [72] Inventors; John v Keith; Hans H Richter both f 2,951,330 9/1960 Bouvet ..57/34 Warwick, 12.1. 3,067,563 12/1962 Van Dijk ..57/34 3,093,282 6/1963 Hezzlewood. ..226/7 I 1 Asslsneel 1mm cwpora'wni Wan/19k, 3,270,933 9/1966 Dekker ..226/97 [-22] FOREIGN PATENTS OR APPLICATIONS l,l40,629 7/1957 France ..242/147 Related 0.5. Application Data [60 1 Division of S61. N0. 537,526, Mar. 25, 1966, Pat. NO. 'f Emmi'ferstanley Gilreath 3,393,880, Continuation of S61. NO. 710,163, Mar. Examiner-Wet?" Schroeder 24 1968 abandoned Att0rneyShaffert and M11161 [52) us. CL .s7/34 11s, 28/62, 25276//1l0966, [57] ABSTRACT [51 Int. Cl. ..D0lh 13/26 A heater for a false twist machine. A strand of yarn passes in a [58] Field of Search ..57/ 34 HS, 58.83, 90, 106, 157 TS, circuitous path through the heater and over guides which pro- 57/157 MS; 28/62; 242/147 A, 153; 19/288; vide a fluid cushion supporting the strand.

[56] References Cited UNITED STATES PATENTS 3,336,738 8/1967 Mattingly et a1 ..57/34 8 Claims 8 Drawing PAIENTEDFEB 1 5 I972 SHEET 1 OF 2 FIGS IN VENTORS SOURCE '0F PRESSURIZED FLUID JOHN v. KEITH HANS H. RICHTER ATTORN'EYS PATENTEUFEB 15 m2 3.641.756

sum 2 0F 2 INVENTORS JOHN V. KEITH HANS H. RICHTER BY Wfll ATToRNYs STRAND HEATING APPARATUS This application is a continuation of US. Ser. No. 710,163, filed Mar. 24, 1968, now abandoned, which itself was a divi sion of application U.S. Ser. No. 537,526, filed Mar. 25, I966 now U.S. Pat. No. 3,393,880, for Strand Control Apparatus".

The invention relates generally to improvements in textile machines and, more particularly, to a novel type of heater for use with false twist machines.

Throughout the present specification and claims, the term yarn is employed in a general sense to indicate any type of attenuated material, and the word package is intended to designate a wound mass of yarn, whatever its form or shape.

In the production of torque stretch yarns," thermoplastic yarn such as nylon or treated natural fibers are drawn from a supply source into a heater and then through a false twist spindle onto a suitable takeup roll or package. Twist imparted by the false twist spindle backs up or migrates through the yarn within the heater, and the heater functions to set this twist. The yarn is subsequently untwisted by the same action of the spindle and the yarn strand then exhibits a bulkiness not naturally characteristic of the yarn being processed. It will be appreciated that is at a given yarn speed a given path length through the heater is necessary, approximately twice this yarn path length through the heater will be necessary should twice the yarn delivery rate be desired. As yarn speeds are multiplied. it becomes highly undesirable and impractical to accommodate the yarn in heaters of conventional design wherein a strand of yarn makes but a single pass therethrough. Attempts have been made heretofore to provide for a plurality of yarn passes through a heater, but such attempts have not been industrially successful.

The invention, in brief, is directed to a false twist heater having guide means over which the yarn is advanced on a cushion of air and between spaced-apart finger or guide elements. Such a cushion of air may serve two functions. First, the cushion of air supports the travelling strand of yarn and tends to minimize or eliminate friction between the yarn and the guide. Second, the flow of air through the yarn guide will maintain the guide at a temperature lower than the temperature of the heater.

Accordingly, an object of the invention is to provide a new and improved heater for strand material.

Another object of the invention is to provide a new and improved false twist heater having yarn guides permitting a plurality of passes of yarn through the heater so that false twist imparted to the yarn by a false twist spindle will pass along the yarn and migrate over the yarn guides.

Other and further objects and advantages will be apparent from the following description and the accompanying drawings, in which:

FIG. I is an exploded perspective view of a guide constructed in accordance with the invention;

FIG. 2 is a perspective view of a winding machine employing the invention;

FIG. 3 is a schematic front elevation view of a rotating takeup roll of the winding machine and illustrates the variation in length of a strand of yarn being traversed or fanned across the surface of the roll;

FIG. 4 is an enlarged fragmentary side elevation view of a compensating arm of the winding machine;

FIG. 5 is a fragmentary side elevation view of a preferred modification of the compensating arm illustrated in FIG. 4;

FIG. 6 is a front elevation view of the compensating arm of FIG. 5;

FIG. 7 is a front elevation view of a stretch yarn machine of the false twist type, illustrating a heater therefor in accordance with the invention; and

FIG. 8 is a sectional view taken along lines 8-8 of FIG. 7.

Referring now to the drawings, FIG. 1 illustrates the pneumatic yarn guide 10 in an exploded condition. The guide includes a pair of finger elements 12. A seal member 14 and a pair of pins l6 provides a base portion 17 ofthe guide. At least one and, if desired, both of the finger elements 12 is formed with a recess or chamber I8 formed at one end thereof. Clearance holes 20 are formed in each of the elements 12, passing through the sidewalls thereof into chambers I8. These clearance holes 20 receive a fastener 22 snugly therethrough which may be a bolt or the like. The fastener is provided with a hollow shank having an inlet 24 and orifices 26 (see FIG. 8) spaced around the circumference in communication with chamber 18. The seal I4 is of such a shape and size as will surround chamber 18 on three sides, but is open on the fourth side leading to the zone between extended finger elements or portions 28. The fastener 22 serves to draw elements I2 together in side-by-side abutting relationship with the distensible seal 14 fixed therebetween. The outer end of fastener 22, i.e., the end opposite the head thereof, is desirably received through an apertured supporting member 29 such as illustrated in FIG. 8 and thereupon secured as by a nut 30 or other suitable closure member. As shown schematically in FIG. 8, the outer end of the hollow fastener 22 is connected to a source of pressurized fluid 32, such as pressurized air.

When the elements 12 are thus clamped together by means of fasteners 22 and 30, it will be appreciated that a space or passage 34 will result between the finger elements 28 from the thickness of seal 14. Of course, the spacing between the extended portions 28 is variable depending upon the thickness and compressibility, if any, of the seal. The passage 34 provides a zone adapted to receive a strand of yarn Y therethrough and the tip ends of extended portions 28 are beveled or rounded for easy reception of the yarn therein.

The pins 16 are tightly held as by a press fit in notches 36 formed in each of the finger elements 12, at opposite ends of the base 17. The pins serve to maintain alignment of the cooperating elements 12. Additionally, since the pins are situated at the outlet of chamber 18 into passage 34, these pins provide guards which act to prevent contact of the yarn with the edges of seal 14, which contact might seriously abrade and perhaps even break the yarn. From what has just been described, it will be apparent that gaseous fluid of any suitable composition is directed under a predetermined pressure through hollow fastener 22. The fluid passes through orifices 26 into chamber 18 which thereby becomes, in effect, a plenum chamber, the fluid therein being at a higher pressure than ambient. The pressurized fluid will then issue from an inlet 38, in the form of an elongated slot which extends between opposite ends 39 of the base 17 and which connects passage 34 with chamber 18 by reason of the discontinuity of seal 14, and will be directed transversely of the path of the yarn. The yarn will thereby be caused to float upon the cushion of pressurized fluid. Although the yarn is restrained in a lateral direction by means of finger portions 28, it has considerable freedom of movement within passage 34 in a direction toward and away from the inlet 38. The pressurized fluid is not only directed axially of the passage 34, but outwardly from the sides thereof so that the yarn will normally be held out of engagement with the pins 16 and even from the sidewalls of finger elements 12.

It will be seen that yarn passing from a supply package to a takeup package and passing through yarn guide 10 will upon increased tension therein, have the tendency to move sideways toward the inlet 38 against the pressurized fluid issuing therefrom. Additional yarn will thereby be paid out and the yarn tension maintained. Oppositely, upon the tendency of yarn tension to decrease, the yarn is urged by the fluid issuing from the yarn guide to move in a sideways direction away from the inlet 38, this action being such as to increase the yarn path length serving to temporarily store the yarn and to maintain tension at a desired level. The air pressure is controllable in any customary manner such that a desired value of yarn tension will always be maintained.

FIG. 2 is illustrative of a conventional takeup machine which has been modified to employ the invention herein disclosed. Said takeup or winding machine may be of the type disclosed in the patent to Keith, earlier cited. In practice with said machine a supply yarn Y is shown flowing from a suitable source (not illustrated). The yarn 42 is traversed to and fro of a core C by traverse means 48 to be wound into a package 44 supported for rotation on a spindle 45. As the yarn Y advances from its supply source to takeup package 44 it is wrapped partially about the strand control apparatus I of the instant invention. In the illustrated embodiment apparatus 10 is supported on a compensating arm 46 which, in turn, is mounted for pivotal movement about a substantially horizontal axis. The control apparatus is attached to the outer, free end of arm 46 by means of hollow bolt 22 and nut 30, and is directed downwardly, that is, in such a manner that the pressurized fluid issuing from inlet 38 is directed substantially downwardly.

In FIG. 4, yarn is seen engaged by the guide 10. The arm 46, so modified, operates in the identical manner disclosed in the aforecited Keith patent to maintain either a substantially constant or a progressively reduced tension in the strand of yarn being would. However, the prior art has produced no known successful method of eliminating the variations in yarn tension as the yarn Y is traversed across the takeup package by means of a first yarn guide 48 or other traversing mechanism. The reason for yarn tension variation is apparent from FIG. 3 which illustrates the winding package 44, and the fanning point from which the yarn is traversed, said fanning point being at apparatus 10 in FIG. 2. Clearly shown in FIG. 3 is the fanning motion effected by the yarn as it winds to and from position Y to Y to Y and returns. As the yarn strand traverses from its disposition at Y to its disposition at either Y to Y the rate of delivery of the yarn onto package 44 is increasing with an accompanying increase in tensile force of the yarn, and vice versa. Furthermore, the tensile force in the yarn is caused to vary a substantial amount at the ends of the package because of the abrupt changes in the winding formation at these reversal points. In the past, when the winding package 44 was rotating at a normal rate of surface speed, the inertia of arm 46 and its conventional yarn guide was found to be too great to effectively follow the varying yarn movements. For such action arm 46 would obviously have to pivot upwards when the yarn path approached the positions of Y and Y and settling downwards when the yarn path approached the disposition of Y Previously, because of the inertia of the arm 46, it has been found that the yarn itself wound extend or stretch to accommodate the changes or fluctuations in yarn path length, the result of which was to impair the quality of the yarn being wound.

This situation is remedied, however, by the use of the control apparatus 10 as shown in FIG. 4. When the yarn approaches the longer yarn path dispositions of either Y or Y;,, and yarn tension increases accordingly, the yarn passing through strand control apparatus 10 is drawn upwards from a position not far from the tip end thereof to a position closer to the inlet 38. At each of the dispositions Y Y and Y and at each of the infinite number of intermediate dispositions which the yarn assumes as it is traversed to and fro of the package, the tension of the yarn is maintained substantially constant. The yarn glides on a cushion of air which has sufficient resilience to accommodate the yarn in all possible traversing dispositions while yet maintaining a single tension value therein during its winding movement.

A preferred modification of the combination compensator arm 46 and yarn guide 10 is compensator arm 52 and its associated mechanism shown in FIGS. and 6. In this instance, a rotatable yarn engaging guide or wheel 54 assists the takeup roll 44 in drawing yarn from the source of supply and delivering it to the package being wound. Rather than being situated in the vertical manner of FIG. 4 with the passage 34 directed downwardly, yarn guide a is horizontally disposed. Therefore, passage 34a opens to the right, as seen in FIG. 5. It will be understood that the apparatus 100 is of generally the same construction as disclosed in FIGS. 1 and 4.

With continuing reference to FIGS. 5 and 6, yarn Y is seen to pass over grooved wheel 54 which is mounted for rotation on its axle 56. In turn axle 56 is suitably mounted on bracket 58 depending from arm 52. The yarn is directed about a guide pin 60, thence through the passage defined by spaced apart extension elements 280, through another slotted yarn guide 62 fixed to bracket 58 at a position above arm 52, and finally is wound onto takeup package 44. Wheel 54 is provided with a plurality of vanes 64 formed about the circumference of an abutted portion 66 thereof. A nozzle 68, connected to source 32 of pressurized fluid, is positioned to direct a jet of fluid against the vanes for rotating the wheel. As in the previous embodiment, pressurized fluid from source 32 is also directed into the yarn receiving passage of yarn guide 10a. Although yarn Y is positively drawn from its source of supply by the takeup roll 44, rotating wheel 54 aids the drawing process, and is particularly effective in reducing yarn tension downstream thereof and increasing tension upstream thereof. This tension difference is adjustable over a wide range by varying the amount of airflow through nozzle 68.

Yarn guide 100 cooperates with wheel 54 to control tension in the identical manner described in the embodiment of FIG. 4. Upon a decrease in yarn tension, as when it approaches path Y (see FIG. 3), fluid issuing forth from chamber 18a impinges on the yarn forcing it toward the tip ends of extension members 280 whereby the yarn is required to assume a longer yarn path, and tension is maintained. Conversely, when yarn tension increases, that is upon approaching paths Y or Y the yarn is drawn toward inlet 38a against the pressurized fluid whereby the yarn path is shortened and tension is again maintained.

Another example of utilization of the invention resides in its combination with heating devices which may take the form disclosed in another Leesona Corporation US. Pat. to W. A. Seem et al., No. 2,864,229, issued Dec. 16, 1958, or may be of any other desired construction. Referring to FIG. 7, reference numeral 70 generally indicates a typical heater which may be employed with conventional yarn texturizing apparatus. Grooved contact elements 72 through which thermoplastic yarn is drawn are heated in a customary fashion and perform to supply heat to the yarn both by conduction and by radia tion. The insulating block 74 and the insulating covers 76 thermally isolate to a substantial degree the path of travel of the yarn from the surrounding atmosphere.

A plurality of grooved elements 72 are illustrated which permit the reversal of yarn being drawn through the heater. Although three such grooves are shown which permit two reversals of direction, as many grooves may be provided as desired, no particular number thereof being critical to the invention. For the effectiveness of the false twist texturizing process, it is desirable that the entire length of yarn present within the confines of the heater 70 be fully effected by the action of a false twist spindle 78, that is, that the twist applied to the yarn in the regions proximate to the false twist spindle should migrate throughout the strand of yarn passing through the heater. The control apparatuses 10 of FIGS. 7 and 8 are constructed and operate in a manner identical to those embodiments previously described. Each control apparatus 10 is located beyond and adjacent one end of the heating surface of the heater and is fixed so as to be stationary with respect to the travelling yarn. A constant yarn tension is maintained throughout the length of yarn passing through the heater. Furthermore, by reason of the nearly unrestrained passage of yarn through and around the yarn guides, twist applied to the yarn by the false twist spindle adjacent one side of the heater progresses throughout the length of yarn located within the confines of the heater and beyond, to a twist restraining element or stop 80 adjacent the other side of the heater.

Use of the invention therefore in combination with the heater of a stretch yarn machine, permits the construction of a much more compact heating unit having a longer passage therethrough for higher yarn speeds without impairing the quality of the yarn.

A novel strand control apparatus has been disclosed herein which operates pneumatically and such that yarn is supported on a cushion of gaseous fluid and is substantially held out of engagement from the guide. Consequently, yarn tension is virtually unchanged from the upstream side to the downstream side thereof, and any condition, such as false twist, applied to the yarn upstream of the guide will be permitted to migrate to the downstream portions of the yarn without a noticeable decrease in that condition. Also disclosed herein is a novel form of pneumatically operated rotatable yarn guide which serves to increase yarn tension on the input side while reducing yarn tension on the output side thereof.

While preferred embodiments of the invention have been disclosed, the description is intended to be illustrative only and it is to be understood that changes and variations may be made without departing from the spirit and scope of the invention as defined by the appended claims.

l claim:

1. Apparatus for processing an advancing strand, comprising a heater, and means for guiding the strand in a circuitous path through the heater, said means including guide means to receive the strand and maintain a cushion of fluid supporting said strand as it passes across the guide means with said guide means having a pair of opposed guide elements extending longitudinally in the same general direction and a base portion between said elements spacing said elements apart to define a restrictive zone for receiving the strand for passage transversely between the guide elements, and inlet means at said base portion to pass said fluid into said zone and against the strand for so supporting the strand on said cushion of air as the strand passes through said zone and effectively preventing the strand from contacting the base portion, with said base portion having opposite ends extending between said guide elements and said guide means being operable for passing said fluid in a direction substantially longitudinal between the elements at an intermediate portion of the base portion and at said opposite ends of the base portion in a direction generally transversely between said elements and across said ends.

2. Apparatus for processing an advancing strand, comprising a heater, and means for guiding the strand in a circuitous path through the heater, said means including guide means to receive the strand and maintain a cushion of fluid supporting said strand as it passes across the guide means with said guide means having a pair of opposed guide elements extending longitudinally in the same direction and a base portion between said elements spacing said elements apart to define a restrictive zone for receiving the strand for passage transversely between the guide elements, and inlet means at said base portion to pass said fluid into said zone and against the strand for so supporting the strand on said cushion of air as the strand passes through said zone and effectively preventing the strand from contacting the base portion, with said base portion having opposite ends extending between said guide elements and said guide means being operable for passing said fluid in a direction substantially longitudinal between the elements at an intermediate portion of the base portion and at said opposite ends of the base portion in a direction generally transversely between said elements and across said ends, with said guide means being operable for substantially reversing the direction of the strand at least once and having guard means at said opposite ends of said base portion for effectively preventing the strand from engaging the base portion.

3. In a false twist machine having a twist stop device and a false twist spindle for processing a strand of yarn advancing through the machine from the twist stop to the spindle, apparatus comprising a heater for receiving and heating the strand as it passes from said twist stop to said false twist spindle, and means for guiding the strand in a circuitous path through the heater, said means including guide means operative to maintain a cushion of fluid supporting said strand with said guide means having a pair of opposed guide elements extending longitudinally in the same general direction and a base portion having opposite ends extending between said elements and spacing said elements apart to define a restrictive zone for receiving the strand for passage across the ends and transversely between the guide elements, and inlet means at said base portion for passing said fluid into said zone and against the strand to so support the strand as it passes through said zone and effectively prevent the strand from contacting the base portion, with said guide means being operable for passing said fluid in a direction substantially longitudinal between the elements at an intermediate portion of the base portion and at said opposite ends of the base portion in a direction transverse between said elements and across said ends.

4. In a false twist machine having a twist stop device and a false twist spindle for processing a strand of yarn advancing through the machine from the twist stop to the spindle, apparatus comprising a heater for receiving and heating the strand as it passes from said twist stop to said false twist spindle, and means for guiding the strand in a circuitous path through the heater, said means including guide means operative to maintain a cushion of fluid supporting said strand with said guide means having a pair of opposed guide elements extending longitudinally in the same general direction and a base portion having opposite ends extending between said elements and spacing said elements apart to define a restrictive zone for receiving the strand for passage across the ends and transversely between the guide elements, and inlet means at said base portion for passing said fluid into said zone and against the strand to so support the strand as it passes through said zone and efiectively prevent the strand from contacting the base portion, with said guide means being operable for passing said fluid in a direction substantially longitudinal between the elements at an intermediate portion of the base portion and at said opposite ends of the base portion in a direction transverse between said elements and across said ends, with said guide means being operable for guiding the strand through a path in which the strand substantially reverses direction at least once and having guard means at said opposite ends of said base portion for effectively preventing the strand from engaging the opposite ends of the base portion.

5. A contact heater having a surface which is maintained at a prescribed temperature for heating a travelling yarn while it is being false twisted comprising in combination heated surface means and guide means located beyond and adjacent one end of said heated surface means, said combination defining a path for said travelling yarn with said path having at least one reversal point, said guide means having means to maintain a cushion of fluid to support said travelling yarn and being located at said reversal point and adapted to reverse the direction of travel of said traveling yarn across said heated surface means to thereby increase the duration of contact between said travelling yarn and said heated surface means.

6. Apparatus as set forth in claim 5 in which said guide means comprises a pair of opposed guide elements extending longitudinally in the same general direction and a base portion between said elements spacing said elements apart to define a restrictive zone for receiving the strand for passage transversely between the guide elements, and inlet means at said base portion to pass said fluid into said zone and against the strand for so supporting the strand on said cushion of air as the strand passes through said zone and effectively preventing the strand from contacting the base portion,

7. In a false twist machine the combination of a twist stop device and a false twist spindle for processing a strand of yarn travelling through the machine from the twist stop to the spindle and a contact heater located in the path of travel of said yarn and having a surface which is maintained at a prescribed temperature for heating said travelling yarn while it is being false twisted, said contact heater comprising in combination heated surface means and guide means located beyond and adjacent one end of said heated surface means and defining a path for said travelling yarn having at least one reversal point, said guide means having means to maintain a cushion of fluid to support said travelling yarn and being located at said reversal point and adapted to reverse the direction of travel of said travelling yarn across said heated surface means to thereby increase the duration of contact between said travelling yarn and said heated surface means.

between the guide elements, and inlet means at said base for passing said fluid into said zone and against the strand to so support the strand as it passes through said zone and effectively prevent the strand from contacting the base.

t I t i 

1. Apparatus for processing an advancing strand, comprising a heater, and means for guiding the strand in a circuitous path through the heater, said means including guide means to receive the strand and maintain a cushion of fluid supporting said strand as it passes across the guide means with said guide means having a pair of opposed guide elements extending longitudinally in the same general direction and a base portion between said elements spacing said elements apart to define a restrictive zone for receiving the strand for passage transversely between the guide elements, and inlet means at said base portion to pass said fluid into said zone and against the strand for so supporting the strand on said cushion of air as the strand passes through said zone and effectively preventing the strand from contacting the base portion, with said base Portion having opposite ends extending between said guide elements and said guide means being operable for passing said fluid in a direction substantially longitudinal between the elements at an intermediate portion of the base portion and at said opposite ends of the base portion in a direction generally transversely between said elements and across said ends.
 2. Apparatus for processing an advancing strand, comprising a heater, and means for guiding the strand in a circuitous path through the heater, said means including guide means to receive the strand and maintain a cushion of fluid supporting said strand as it passes across the guide means with said guide means having a pair of opposed guide elements extending longitudinally in the same direction and a base portion between said elements spacing said elements apart to define a restrictive zone for receiving the strand for passage transversely between the guide elements, and inlet means at said base portion to pass said fluid into said zone and against the strand for so supporting the strand on said cushion of air as the strand passes through said zone and effectively preventing the strand from contacting the base portion, with said base portion having opposite ends extending between said guide elements and said guide means being operable for passing said fluid in a direction substantially longitudinal between the elements at an intermediate portion of the base portion and at said opposite ends of the base portion in a direction generally transversely between said elements and across said ends, with said guide means being operable for substantially reversing the direction of the strand at least once and having guard means at said opposite ends of said base portion for effectively preventing the strand from engaging the base portion.
 3. In a false twist machine having a twist stop device and a false twist spindle for processing a strand of yarn advancing through the machine from the twist stop to the spindle, apparatus comprising a heater for receiving and heating the strand as it passes from said twist stop to said false twist spindle, and means for guiding the strand in a circuitous path through the heater, said means including guide means operative to maintain a cushion of fluid supporting said strand with said guide means having a pair of opposed guide elements extending longitudinally in the same general direction and a base portion having opposite ends extending between said elements and spacing said elements apart to define a restrictive zone for receiving the strand for passage across the ends and transversely between the guide elements, and inlet means at said base portion for passing said fluid into said zone and against the strand to so support the strand as it passes through said zone and effectively prevent the strand from contacting the base portion, with said guide means being operable for passing said fluid in a direction substantially longitudinal between the elements at an intermediate portion of the base portion and at said opposite ends of the base portion in a direction transverse between said elements and across said ends.
 4. In a false twist machine having a twist stop device and a false twist spindle for processing a strand of yarn advancing through the machine from the twist stop to the spindle, apparatus comprising a heater for receiving and heating the strand as it passes from said twist stop to said false twist spindle, and means for guiding the strand in a circuitous path through the heater, said means including guide means operative to maintain a cushion of fluid supporting said strand with said guide means having a pair of opposed guide elements extending longitudinally in the same general direction and a base portion having opposite ends extending between said elements and spacing said elements apart to define a restrictive zone for receiving the strand for passage across the ends and transversely between the guide elements, and inlet means at said base portion for passing said fluId into said zone and against the strand to so support the strand as it passes through said zone and effectively prevent the strand from contacting the base portion, with said guide means being operable for passing said fluid in a direction substantially longitudinal between the elements at an intermediate portion of the base portion and at said opposite ends of the base portion in a direction transverse between said elements and across said ends, with said guide means being operable for guiding the strand through a path in which the strand substantially reverses direction at least once and having guard means at said opposite ends of said base portion for effectively preventing the strand from engaging the opposite ends of the base portion.
 5. A contact heater having a surface which is maintained at a prescribed temperature for heating a travelling yarn while it is being false twisted comprising in combination heated surface means and guide means located beyond and adjacent one end of said heated surface means, said combination defining a path for said travelling yarn with said path having at least one reversal point, said guide means having means to maintain a cushion of fluid to support said travelling yarn and being located at said reversal point and adapted to reverse the direction of travel of said traveling yarn across said heated surface means to thereby increase the duration of contact between said travelling yarn and said heated surface means.
 6. Apparatus as set forth in claim 5 in which said guide means comprises a pair of opposed guide elements extending longitudinally in the same general direction and a base portion between said elements spacing said elements apart to define a restrictive zone for receiving the strand for passage transversely between the guide elements, and inlet means at said base portion to pass said fluid into said zone and against the strand for so supporting the strand on said cushion of air as the strand passes through said zone and effectively preventing the strand from contacting the base portion.
 7. In a false twist machine the combination of a twist stop device and a false twist spindle for processing a strand of yarn travelling through the machine from the twist stop to the spindle and a contact heater located in the path of travel of said yarn and having a surface which is maintained at a prescribed temperature for heating said travelling yarn while it is being false twisted, said contact heater comprising in combination heated surface means and guide means located beyond and adjacent one end of said heated surface means and defining a path for said travelling yarn having at least one reversal point, said guide means having means to maintain a cushion of fluid to support said travelling yarn and being located at said reversal point and adapted to reverse the direction of travel of said travelling yarn across said heated surface means to thereby increase the duration of contact between said travelling yarn and said heated surface means.
 8. Apparatus as set forth in claim 7 in which said guide means comprising a pair of opposed guide elements extending longitudinally in the same general direction and a base having opposite ends extending between said elements and spacing said elements apart to define a restrictive zone for receiving the strand for passage across the ends and transversely between the guide elements, and inlet means at said base for passing said fluid into said zone and against the strand to so support the strand as it passes through said zone and effectively prevent the strand from contacting the base. 